Basically everything you can do to stick with primal, the better off you'll be. If that means 80% of the time you're primal in diet and 20% of the time you're not, you're still better off than you would be with a regular diet and lifestyle.

Personally I wouldn't interpret the 80/20 rule as a literal percentage suggestion, but more of a general statement that you can cut yourself some slack so you don't get overwhelmed by the idea of strictness.

Later as the transition difficulties ease, it'll come naturally to be more strict with it -- for example, my husband (who's more Primal than I am right now) has been surprised to find that his eternal sweet tooth is easing. He wasn't planning to commit this much to Primal eating, but he's found that he is just not interested in soda and ice cream anymore, it all tastes too sweet. We take this as a sign that his body's adjusting well!

I just started (with the Primal Leap kit) and my only 20% has been a glass or two of red wine a night and it's working like a charm. I wouldn't get too into the percentages though as I think you could really mess it up if you did.

Since 20% is a mathematical concept, you could look at it as follows:
Say you're perfect daily intake approximated 2,000 calories. For a week that would be 14,000 calories. 14,000 x 20% = 2,800. I don't think things will work well if you "splurged" for a total of 2,800 calories a week, but maybe I'm wrong. My wine 20% adds up to about 25% of that number a week.

Realistically, when my 30 day leap period is over, my 20% may be a drink here or there or a meal out with friends/family when I enjoy non-primal fare and I'll see how I look and feel by doing that.

I just started (with the Primal Leap kit) and my only 20% has been a glass or two of red wine a night and it's working like a charm. I wouldn't get too into the percentages though as I think you could really mess it up if you did.

My 20% is the dark chocolate, usually daily. It has to fit in with my carb count though from now on. I have to plan my meals first and see if there is room left and how much.

Otherwise, don't have any desire to eat pasta, bread, rice....(apart from a wee slice of banana bread my flatmate made)

I don't think it actually matters that much how you view it. My interpretation of the 80/20 rule is that you should do the best you can and not beat yourself up if you sometimes have something that is not strictly primal. So many diets can lead to an all or nothing mentaility and in the past if I 'fell off the wagon' I'd often get caught in a ongoing cycle - " oh well I've cheated already today so I may as well have x as well and start back again properly tomorrow, next week, whenever...". On the PB I allow myself to have something 'off plan' if I really want it and then get on with striving for 100% again. The key for me is that I have to actively choose to eat it (and hopefully enjoy it), and not just eat it mindlessly. Funnily enough, now that I know I've told myself I can have a piece of cake if I really, really want it, more often than not I find myself thinking I didn't really want any anyway.

Later as the transition difficulties ease, it'll come naturally to be more strict with it -- for example, my husband (who's more Primal than I am right now) has been surprised to find that his eternal sweet tooth is easing. He wasn't planning to commit this much to Primal eating, but he's found that he is just not interested in soda and ice cream anymore, it all tastes too sweet. We take this as a sign that his body's adjusting well!